1) Don't mess with Raid-0 unless you don't care about any of your data or hours lost rebuilding systems due to a single drive failure.
2) Don't mess with Write caching unless you have (2) SSD's running in a Raid-1 config. SSD's fail/wear-out and you will have no advanced warning
3) Create a single Raid-6 group with 8 Drives (which are on QNAP's compatibility list) + a UPS for power stability and call it a day.

Unless you have 10GbE networking, it likely won't matter anyway. But since you haven't mentioned what you are going to use this for, see items 1-3

Yeah I already have a 10gbe Network, and I have an old Drobo which I already back everything up onto, and I have another windows server with 4 bays that I can backup onto as well.

I'm ok with one disk failing, I can restore from my drobo / windows server / and I also have tape backups set up as well although I'd hate to restore from them.

What I want is when I'm running to the airport, and I suddenly realize I forgot some large set of files, that I can copy it off my share onto my travel USB SSD without missing my fight.

(and I want all my efforts of setting up a 10gbe to actually pay off somehow...)

I'm also not worried about the write-cache failing, as long as I just have to re-start the file transfer whenever that happens. My old RAID has a 4GB ram write cache and SSD write cache that I never had any issues with. That server is just so old, so I deiced to upgrade to something (physically) smaller.

After thinking about it, I'm going to do 4 drives in Raid Zero on my one server and 5 drives in Raid 0 on my QNAS. When I run out if space I'll add bigger drives to the windows server and add more drives to the QNAS. I'll see how long it takes to copy with the two arrays and 10gbe.

Hi dmyze -
I think because people like me have a lot of experience (and so does Trexx) - when I see questions like this - I say "are you kidding me" -
but I did not respond until I wehn to your link on Stack Exchange.

Is there a performance difference between a RAID with 2 drives and with 16 drives ? OF COURSE THERE IS, but if you have no experience in doing so, then you just don't know.
I had a gentlemen contact me from India, who simply could not understand why he was getting such poor performance from his QNAP over a 10G network, while using only one SSD drive.
I think I wound up "insulting him" because he felt he was very knowlegable about all of this, and could not understand why he needed to use multiple SSD's in a RAID group to get good performance for his
workgroup. Needless to say - he never wound up hiring me. I guess I was rude, because I could not give him a sufficient answer on why one single SSD could not be enough for his entire workgroup with his QNAP.

Bottom line - stop reading all this stuff on line. (I feel like this is me, when I go to my doctors office, and try to tell him what medicine works, and does not work, based on what I read on the internet).
I don't know what your application is, but if you put EIGHT drives in a DECENT QNAP model (no Annapurna models - I don't care what QNAP says or shows on their website) - you will get great performance ovver 10G, be it RAID 0, RAID 5 or RAID 6.

With eight 7200 RPM drives on a model like the TVS-872XT, you will get over 800 MB/sec with a 10G connection. With the same drives, in a QNAP TS-832X, you will barely get 200 MB/sec with the same computer, and the same RAID configuration. How do I know this ? I do this every day.

For 8-th bay NAS I would use it in one of three ways:
1. Two SSD in RAID1 for OS and apps only. Six HDD in RAID5 for data. This way you have the protection, speed and performance. RAID0 is delayed waste of many hours or days time for recreating everything. RAID6 is unnecessary waste of disk space and CPU power without substantial increase of availability or protecting. RAID6 rebuild time is long and it takes more CPU power to write. Better have backups. This setup I use and it's fast for Roon database and Plex video files.
2. Eight HDD in RAID5. This way you don't have the speed with databases and small files but it's faster for large amount of data and the best way to saturate 10Gbps.
3. If you like to live your life fast and dangerously use one SSD for system volume and apps and seven HDD for data in RAID0. Have daily backup of everything. I don't know if you can backup whole partition with system files? Maybe taking discs out and make image of whole drive?

SSD will add speed only in specific scenario like database or web server. It's useless for large files like few TB video library - fastest will be RAID0 and RAID5 second.